Coated particles

ABSTRACT

It is an object of the invention to provide coated particles excellent in the reliability of connection.  
     The invention provides coated particles each comprising a metal-surfaced particle as a core and resulting from a partial surface modification of that core particle with an organic compound via a functional group (A) capable of binding to a metal.

TECHNICAL FIELD

[0001] The present invention relates to coated particles.

BACKGROUND ART

[0002] Anisotropic conductive particles for electric connection are usedin electrode-connecting materials for liquid crystal display panels andin anisotropic conductive films in mounting LSI chips. Such anisotropicconductive films that are in use are produced, for example, bydispersing metal-plated particles in an insulating material and moldingthe dispersion into film-like forms. When such an anisotropic conductivefilm is inserted between electrodes and heated under pressure, theinsulating material melts and the metal-plated particles serve asconductive particles and the electrodes are electrically connected toeach other.

[0003] However, with the recent trend toward finer interelectrodepitches, it becomes necessary to increase the level of addition ofconductive particles in the anisotropic conductive films for securinghigh levels of connection reliability. This results, however, intransverse conduction by neighboring particles, for instance, and suchproblems as short circuiting between neighboring electrodes arise. Foralleviating such problems, Japanese Kokai Publication Sho-62-40183, forinstance, describes a method which comprises coating metal-platedparticles with a resin incompatible with the film layer resin andgrinding the resulting mass to give particles, while Japanese KokaiPublication Hei-08-335407 describes a method which comprises coatingmetal-plated particles by microencapsulation. However, the methodsmentioned above have drawbacks. Thus, the strength of bonding betweenthe resin used for coating and the metal is weak, since the resin isonly physically adsorbed on the metal-plated particles. In the step ofgrinding the aggregated particles into single and individual particlesafter coating treatment, the coating resin may be peeled off or thecoating resin thickness may decrease, so that the metal-plated particlesurface may be exposed, not only conduction in the electrode directionbut also conduction in the transverse direction may occur, increasingshort circuiting in the transverse direction. Another drawback of theabove methods is that since a resin is layered on the metal particlesurface, the laminate resin may be peeled off also in the step ofkneading the coated particles with a binder resin or an adhesive.Furthermore, the resin may be peeled off from the coated particlesurface even in the step of thermocompression bonding of the coatedparticle-containing anisotropic conductive film at elevatedtemperatures.

SUMMARY OF THE INVENTION

[0004] In view of the state of the art as discussed hereinabove, it isan object of the present invention to provide coated particles excellentin the reliability of connection.

[0005] The present invention consists in coated particles eachcomprising a metal-surfaced particle as a core and resulting from apartial modification of the surface thereof with an organic compound viaa functional group (A) capable of binding to a metal as bound thereto.

[0006] Preferred as the coated particles of the invention are thoseresulting from grafting of an organic compound onto the metal-surfacedparticle surface or those each comprising a metal-surfaced particle as acore and resulting from partial modification of the surface thereof withorganic particles containing a functional group (A) capable of bindingto the metal.

[0007] In cases where the coated particles of the invention eachcomprises a metal-surfaced particle with an organic compound graftedonto the surface thereof, the coated particles of the invention arepreferably produced by introducing a compound containing a polymerizingor chain-transferring functional group or catalyst moiety (C) onto thesurface of each metal-surface particle serving as a core, followed bygraft polymerization with each polymerizing or chain-transferringfunctional group or catalyst moiety (C) as an initiation site forpartial modification of the particle surface with an organic compound.

[0008] The above-mentioned graft polymerization is preferably carriedout in the manner of metathesis polymerization. In particular, thetechnique of ring-opening metathesis polymerization using a cyclicmonomer is preferred since the reaction procedure is easy to carry out.

[0009] The above-mentioned organic compound is preferably chargedpositively or negatively. The organic compound is preferably aninsulating compound.

DETAILED DISCLOSURE OF THE INVENTION

[0010] In the following, the present invention is described in detail.

[0011] By saying “partial surface modification with an organic compound”herein, it is meant that the whole surface is not completely coveredwith that organic compound.

[0012] The coated particles of the invention each comprises, as a core,a particle whose surface is made of a metal (herein referred to as“metal-surfaced particles”)

[0013] The above-mentioned metal is not particularly restricted but mayhave conductivity. Thus, it includes, among others, such metals as gold,platinum, silver, copper, iron, nickel, aluminum, and chromium; andmetal compounds such as ITO and solder. Among them, gold is judiciouslyused because of its low resistance value.

[0014] The above-mentioned metal-surfaced particle is not particularlyrestricted provided that the outermost layer is made of a metal. Thus,it may be a particle made of such a metal as mentioned above alone, or aparticle which is obtainable by formation of a layer of such a metal asmentioned above or a surface of a core particle made of an organic orinorganic compound by vapor deposition, plating, coating or any otherappropriate technique.

[0015] The coated particles of the invention can be obtained by partialsurface modification of such metal-surfaced particles to serve as coreswith an organic compound via a functional group (A) capable of bindingto the metal.

[0016] The functional group (A) capable of binding to the metal is notparticularly restricted but may be any of those groups capable offorming an ionic bond, covalent bond or coordinate bond with the metal.Thus, it includes, among others, silane, silanol, carboxyl, amino,ammonium, nitro, hydroxyl, carbonyl, thiol, sulfonic acid, sulfonium,boric acid, oxazoline, pyrrolidone, phosphoric acid and nitrile groups.Since the use of a coordinate bond is suited to coupling to metals, S, Nor P atom-containing groups are judiciously used. When the metal isgold, for instance, a thiol group capable of forming a coordinate bondwith gold is judiciously used.

[0017] The organic compound is not particularly restricted but includes,among others, (un)saturated hydrocarbons, aromatic hydrocarbons,(un)saturated fatty acids, aromatic carboxylic acids, (un)saturatedketones, aromatic ketones, (un)saturated alcohols, aromatic alcohols,(un)saturated amines, aromatic amines, (un)saturated thiols, aromaticthiols, organosilicon compounds, derivatives of these, condensationproducts derived from one or more of these, and polymers derived fromone or more of these. The term “(un)saturated” used above means“saturated and unsaturated”.

[0018] As the above-mentioned condensation products or polymers, theremay be mentioned, for example, polyolefins such as polyethylene andpolybutadiene; polyethers such as polyethylene glycol and polypropyleneglycol; polystyrene, poly(meth)acrylic acid, poly(meth)acrylic acidesters, poly(vinyl alcohol), polyvinyl esters, phenolic resins, melamineresins, allylic resins, furan resins, polyesters, epoxy resins, siliconeresins, polyimide resins, polyurethanes, Teflon, acrylonitrile-styreneresins, styrene-butadiene resins, vinyl resins, polyamide resins,polycarbonates, polyacetals, polyethersulfones, polyphenylene oxide,sugars, starch, cellulose, and polypeptides. These organic compounds maybe used singly or two or more of them may be used combinedly.

[0019] In cases where the coated particles of the invention are used asanisotropic conductive particles, the above organic compound ispreferably selected from among insulating compounds.

[0020] The method of partial modification with such an organic compoundas mentioned above is not particularly restricted but may be any methodcapable of coupling the organic compound to the metal surface via afunctional group (A). Thus, there may be mentioned the method comprisinggrafting the organic compound onto the metal surface, the methodcomprising coupling organic particles containing a functional group (A)capable of binding to the metal, and the method comprising coating themetal surface with an organic compound and then providing the coatingwith micropores, for instance.

[0021] Among them, the method comprising grafting an organic compoundonto the metal surface and the method comprising coupling organicparticles containing a functional group (A) capable of binding to themetal are judiciously used.

[0022] Thus, the coated particles of the invention can be obtained bygrafting an organic compound onto the surface of metal-surfacedparticles.

[0023] The method of grafting an organic compound onto the surface ofmetal-surfaced particles is not particularly restricted but includes,among others, 1) the method comprising providing the organic compoundwith a functional group (A) capable of binding to the metal andintroducing the resulting compound onto the metal surface, 2) the methodcomprising reacting a compound containing a functional group (A) capableof binding to the metal and a reactive functional group (B) capable offorming a covalent bond by a chemical reaction, for example a hydroxyl,carboxyl, amino, epoxy, silyl, silanol or isocyanato group, with themetal surface and then substituting the reactive functional group (B)for the organic compound by a single-stage or multistage reaction, and3) the method comprising introducing a compound containing apolymerizing or chain-transferring functional group or catalyst moiety(C) onto the surface of metal-surfaced particles via a functional group(A) capable of binding to the metal as bound thereto and carrying outgraft polymerization with each polymerizing or chain-transferringfunctional group or catalyst moiety (C) serving as an initiation site.

[0024] Among them, the method 3) involving graft polymerization isjudiciously used.

[0025] Thus, the coated particles of the invention can be obtained byintroducing a compound containing a polymerizing or chain-transferringfunctional group or catalyst moiety (C) onto the surface ofmetal-surfaced particles via a functional group (A) capable of bindingto the metal as bound thereto and carrying out graft polymerization witheach polymerizing or chain-transferring functional group or catalystmoiety (C) site serving as an initiation site.

[0026] The polymerizing or chain transferring functional group orcatalyst (C) mentioned above is a functional group or catalystfunctioning as a graft polymerization initiating site and includes,among others, radically cleavable groups such as azo and perestergroups; chain transfer groups such as thiol, sulfide, dithiocarbamate,nitroxyl and halogen groups; unsaturated bond-containing groups such asvinyl, alkenyl and acetylene groups; cyclic groups such as cyclic ether,cyclic formal, lactone, lactam, cyclic iminoether, cyclic olefin, cyclicsiloxane and cyclic phosphazene groups; aldehyde, ketone, isocyanato,hydroxyl, amino and carboxyl groups; and halogen compounds, oxyhalogencompounds and organic ammonium salts having one or more central metalseach selected from among Li, Na, Mg, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb,Mo, Ru, Hf, Ta, W, Re, Os, and Ir; and organometallic compounds.

[0027] In cases where the above graft polymerization is carried out inthe manner of ring-opening metathesis polymerization, however, use ismade, as the above-mentioned polymerizing or chain transferringfunctional group or catalyst (C), of a metathesis reaction catalyst suchas a chloride having, as a central metal, one species selected fromamong Ti, V, Cr, Zr, Nb, Mo, Ru, Ta, W, Re, Os and Ir, an organometalliccompound, an alkylidene complex, a vinylidene complex or a like carbenecomplex or a carbyne complex. As specific examples of the metathesisreaction catalyst, there may be mentioned metal chlorides such as TiCl₄,VOCl₃, MoCl₅, ReCl₅, IrCl₃, ZrCl₄, NbCl₅, WCl₆, RuCl₃, VCl₄, TaCl₅,WOCl₄ and OsCl₃, organometallic compounds such as tridecylammoniummolybdate, and organometallic complexes such asbis(tricyclohexylphosphine)benzylideneruthenium(IV) dichloride. Amongthese, those in which the central metal is ruthenium are judiciouslyused.

[0028] The above graft polymerization may be carried out in the mannerof radical polymerization, ionic polymerization, coordinationpolymerization, metathesis polymerization, polycondensation reaction orpolyaddition reaction, for instance, according to the polymerizing orchain transferring functional group or catalyst (C) employed. Amongthese, the techniques of living radical polymerization, anionicpolymerization, cationic polymerization, and metathesis polymerization,by which the polymer chain length can be controlled, are judiciouslyused. In particular, ring-opening metathesis polymerization is morepreferred because of the ease of the reaction procedure.

[0029] In ring-opening metathesis polymerization, the polymer chainlength can be controlled in a relatively easy manner and the catalystmetal can be removed with ease and, unlike living polymerization, nohalogen or like living controlling group will remain at any molecularterminus.

[0030] The monomer to be subjected to the above graft polymerization isnot particularly restricted but may be any of those monomers which arepolymerizable, for example in the manner of radical polymerization,ionic polymerization, ring-opening polymerization, isomerizationpolymerization, cyclization polymerization, elimination polymerization,polyaddition, polycondensation, or addition condensation. Thus, itincludes, among others, ethylene, butadiene, styrene derivatives;(meth)acrylic acid, ester derivatives or amide derivatives thereof;vinyl group-containing compounds such as vinyl ester derivatives andvinyl ether derivatives; cyclic olefin-containing compounds such ascyclooctadiene and norbornene derivatives; cyclic ethers such asethylene oxide derivatives, tetrahydrofuran derivatives and trioxanederivatives; cyclic acetals such as 1,3-dioxepane derivatives and4H,7H-1,3-dioxepin; cyclic esters such as ε-caprolactone, glycolide andtrimethylene carbonate; cyclic amines such as aziridine and1-methylazetidine; cyclic sulfides such as propylene sulfide; oxazolinederivatives; lactams such as azetidinone, pyrrolidone and ε-caprolactam;cyclic siloxanes such as hexamethylcyclotrisiloxane; cyclic phosphazenessuch as hexachlorophosphazene; aldehydes such as formaldehyde andacetaldehyde; phenol derivatives; aniline derivatives; isocyanatogroup-containing compounds such as hexamethylene isocyanate; hydroxylgroup-containing compounds such as ethylene glycol and tetramethyleneglycol; amino group-containing compounds such as hexamethylenediamine;carboxyl group-containing compounds such as adipic acid and terephthalicacid; amino acid derivatives; and urea derivatives. These monomers maybe used singly or two or more of them may be used in combination.

[0031] In cases where the above graft polymerization consists inmetathesis polymerization, however, the monomer to be subjected to graftpolymerization is preferably one capable of metathesis polymerization.Preferred are monocyclic olefins and derivatives thereof, such ascyclobutene, cyclopentene, cyclooctene and cyclooctadiene; polycyclicolefins and derivatives thereof, such as norbornene, norbornadiene,dicyclopentadiene and tricyclopentadiene; and hetero atom-containingcyclic olefins such as 2,3-dihydrofuran,exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride,9-oxabicyclo[6.1.0]non-4-ene,exo-N-methyl-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide and1,4-dihydro-1,4-epoxynaphthalene, among others. These monomers may beused singly or two or more of them may be used in combination.

[0032] In carrying out the above-mentioned graft polymerization, theorganic compound to be used for surface modification of metal-surfacedparticles preferably has a positive or negative charge. When the organiccompound is positively or negatively charged within the molecule,repulsion occurs among organic compound molecules and intramolecularly,so that graft density control becomes easy in the step of grafting themonto the metal-surfaced particles. Furthermore, the aggregation ofconductive particles can be avoided and the dispersibility thereof inthe binder resin is also improved. For the above-mentioned organiccompound to have a positive or negative charge within the molecule, itis preferred the molecule has a functional group on its side chainand/or at its terminus. The functional group includes ammonium,sulfonium, sulfonic acid, carboxyl, phosphoric acid, boric acid andnitrile groups, and salts of these, for instance.

[0033] The method of introducing such a functional group is notparticularly restricted but may be the one comprising copolymerizing amonomer having such a functional group in the step of carrying out thepolymerization reaction or the one comprising introducing such afunctional group into side chains by a chemical reaction afterpolymerization.

[0034] In carrying out the above-mentioned graft polymerization, a chaintransfer agent, a catalyst, a promoter and/or the like may be usedaccording to need. In cases where the polymerizing or chain-transferringfunctional group or catalyst moiety (C)-containing compound is a metalchloride or an organometallic compound, organoaluminum compounds such astriethylaluminum, alkyllithiums such as butyllithium, organotincompounds such as dimethyltins, phenyldiazomethane, and methyldiazoacetate, for instance, may be used as the promoter.

[0035] The above polymerizing or chain-transferring functional group orcatalyst moiety (C)-containing compound may be an organic compound or aninorganic compound.

[0036] The method of introducing the polymerizing or chain-transferringfunctional group or catalyst moiety (C)-containing compound onto thesurface of the metal-surface particles is not particularly restrictedbut includes, among others, 3-1) the method comprising causing thepolymerizing or chain-transferring functional group or catalyst moiety(C)-containing compound to contain a functional group (A) capable ofbinding to the metal and introducing the resulting compound onto themetal surface, 3-2) the method comprising reacting a compound containinga functional group (A) capable of binding to the metal and a reactivefunctional group (B) with the metal-surfaced particles and thensubstituting the reactive functional group (B) for the polymerizing orchain-transferring functional group or catalyst moiety (C) in one stepor in a plurality of steps, and 3-3) the method comprising reacting acompound containing a group (A) capable of binding to the metal-surfacedparticles with the metal-surfaced particles, then modifying the surfacewith a reactive functional group (B) by plasma treatment, for instance,and, further, substituting the reactive functional group (B) for thepolymerizing or chain-transferring functional group or catalyst moiety(C) in one step or in a plurality of steps.

[0037] The compound to be used in introducing the polymerizing orchain-transferring functional group or catalyst moiety (C)-containingcompound onto the surface of the metal-surfaced particles according tothe above-mentioned method 3-1) is not particularly restricted but maybe any of those which has a group (A) capable of binding to themetal-surfaced particles and a polymerizing or chain-transferringfunctional group or catalyst moiety (C) in one and the same molecule,for example 2,2′-azobisisobutyronitrile, 2,2′-azobisamidinodipropanedihydrochloride, mercaptophenol, mercaptohexanol, thiol-terminatedpoly(vinyl alcohol), 4-hydroxyphenyldimethylsulfonium methyl sulfate,mercaptopropionic acid, 2,2′-bipyridine-4,4′-dicarboxylic acid, thiocticacid, 4-imidazoleacetic acid, histidine, cysteine, methionine,p-mercaptostyrene, sodium p-styrenesulfonate, p-dimethylsulfoniophenylmethacrylate methyl sulfate, acrylonitrile, sodiumbis(tricyclohexylphosphine)-p-sulfonato-benzylideneruthenium(IV)dichloride, and the like.

[0038] The above-mentioned method 3-2) of introducing the polymerizingor chain-transferring functional group or catalyst moiety (C)-containingcompound onto the surface of the metal-surfaced particles is notparticularly restricted but may be, for example, the one comprisingintroducing a compound having a reactive functional group (B), such ashydroxyl, carboxyl, amino, epoxy, silyl, silanol or isocyanato group,and a functional group (A) capable of binding to the metal onto themetal surface and then reacting the reactive functional group (B) with acompound having a functional group capable of covalent bonding with thereactive functional group (B) and having the polymerizing orchain-transferring functional group or catalyst moiety (C) to therebyeffect the introduction of the polymerizing or chain-transferringfunctional group or catalyst moiety (C).

[0039] Specifically, there may be mentioned, among others, the methodcomprising introducing hydroxyl groups onto the metal-surfaced particlesusing mercaptophenol and then converting the groups to chlorosulfonylgroups, which are chain-transferring functional groups (C), by silanecoupling using 2-(4-chlorosulfonyl)ethyltrichlorosilane; the methodcomprising introducing hydroxyl groups onto the metal-surfaced particlesusing 4-hydroxyphenyldimethylsulfonium methyl sulfate and convertingthose groups to vinyl groups, which are polymerizing functional groups(C), by esterification condensation using methacryloyl chloride; themethod comprising introducing amino groups onto the metal-surfacedparticles using histidine and then converting the same to chloro groups,which are chain-transferring functional groups (C), by addition reactionusing 4-(chloromethyl)phenyl isocyanate; and the method comprisingintroducing hydroxyl groups onto the metal-surfaced particles usingmercaptoundecanol, then converting the same to norbornene groups bysilane coupling using 2-norbornene-6-methyldichlorosilane and, further,converting the same to ruthenium groups, which are chain-transferringcatalyst (C) moieties, through coordination ofbis(tricyclohexylphosphine)benzylideneruthenium(IV) dichloride.

[0040] The above-mentioned method 3-3) of introducing a compound havinga polymerizing or chain-transferring functional group or catalyst moiety(C) onto the surface of the metal-surfaced particles is not particularlyrestricted but may be, for example, the method comprising introducing acompound having a functional group (A) capable of binding to the metalonto the metal-surfaced particles, then modifying a part of the compoundinto a reactive functional group (B) by plasma treatment or oxidationtreatment, for instance, and converting the same to a polymerizing orchain-transferring functional group or catalyst moiety (C) by the methodshown above with respect to the method 3-2).

[0041] The coated particles of the invention can also be obtained by themethod comprising binding, to the metal surface, organic particlescontaining a functional group (A) capable of binding to the metal.

[0042] The above-mentioned organic particles are particles constitutedof the above-mentioned organic compound.

[0043] When the partial surface modification is carried out using theorganic particles mentioned above, the tendency for the conductiveparticles after modification to aggregate is weak, so that the load onthe particles in the disaggregation step for rendering them single andindividual is light and the coating organic compound is hardly peeledoff.

[0044] The organic particles preferably have a positive or negativecharge superficially or internally so that they may repulse one anotherbut may not aggregate with one another.

[0045] The method of charging them positively or negatively is notparticularly restricted but includes, among others, the methodcomprising admixing an organic or inorganic ionic compound with theabove-mentioned organic particles in the step of production thereof, themethod comprising introducing such compound onto the surface of theorganic particles by chemical bonding, the method comprising introducingsuch compound onto the surface of the organic particles by physicaladsorption, the method comprising ionically modifying the surface of theorganic particles by chemical treatment, and the method comprisingionically modifying the surface of the organic particles by means ofplasma or the like.

[0046] The method of causing the organic particles to contain afunctional group (A) capable of binding to the metal is not particularlyrestricted but includes, among others, the method comprising admixingthe same with the organic particles in the step of production thereof,the method comprising introducing the same onto the surface of theorganic particles by chemical bonding, the method comprising introducingthe same onto the surface of the organic particles by physicaladsorption, the method comprising modifying the surface of the organicparticles by chemical treatment to provide that surface with groupscapable of binding to the metal, and the method comprising modifying thesurface of the organic particles by means of plasma or the like toprovide that surface with groups capable of binding to the metal.

[0047] The particle diameter of the organic particles is notparticularly restricted but, when the coated particles of the inventionare used as anisotropic conductive particles, it is preferably withinthe range of 1 to 2,000 nm. Within this range, the insulation betweenneighboring conductive particles can be secured and, when the coatedparticles of the invention are mutually adhered under pressure,conduction is realized.

[0048] The method of producing the above organic particles is notparticularly restricted but may be any of the methods known in the art,for example, emulsion polymerization, soap-free precipitationpolymerization, dispersion polymerization, suspension polymerization,and crushing of a cured resin.

[0049] The thickness of the organic layer on the coated particles of theinvention as formed upon modification with the above-mentioned organiccompound is not particularly restricted but may vary according to themodified area and other factors. When the coated particles of theinvention are used as anisotropic conductive particles, however, thethickness is preferably 1 to 2,000 nm. Within this range, the insulationbetween neighboring conductive particles can be secured and, when thecoated particles of the invention are mutually adhered under pressure,conduction is realized.

[0050] The percentage of the area on the coated particles of theinvention as modified by the above-mentioned organic compound is notparticularly restricted but may vary according to the molecular weightand structure of the modifying organic compound and the thickness of theorganic layer, among others. Generally, however, it is preferably 10 to90% of the surface area of the metal-plated particles. Within thisrange, the insulation between neighboring conductive particles can besecured when the coated particles of the invention are used asanisotropic conductive particles and, when the coated particles of theinvention are mutually adhered under pressure, conduction is realized. Amore preferred range is 20 to 90%.

[0051] The coated particles of the invention each of which comprises ametal-surface particle as a core with the surface thereof partiallymodified with the organic compound via a functional group (A) capable ofbinding to the metal as bound thereto are strong in the strength ofbonding between the coating organic layer and the metal, so that theorganic layer can hardly be peeled off. Therefore, when the coatedparticles of the invention are used as anisotropic conductive particles,high levels of connection reliability can be secured while maintainingthe insulation between neighboring particles.

[0052] In cases where the surface of the metal-surfaced particles ismodified with the organic compound by means of grafting, themodification area and thickness can easily be controlled, so that themodification can be adapted to the conditions of use of the coatedparticles. Furthermore, when the surface of the metal-surfaced particlesis modified by the organic compound by means of graft polymerization,the monomer to be used can be selected, with the result that it becomeseasy to control the layer structure and provide such functions asadhesiveness, tendency toward no aggregation, hydrophobicity andhydrophilicity; excellent performance characteristics can thus beexhibited.

BEST MODE FOR CARRYING OUT THE INVENTION

[0053] The following examples illustrate the present invention in moredetail. These examples are, however, by no means limitative of the scopeof the invention.

EXAMPLE 1

[0054] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 g of commercially available, thiol group-terminatedpoly(vinyl alcohol) (average molecular weight 20,000) was dissolved in500 g of distilled water in an argon atmosphere.

[0055] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreacted poly(vinylalcohol) was removed by filtration, the particles were washed with hotwater and then dried to give coated particles with the surface thereofpartially modified by the insulating organic compound.

EXAMPLE 2

[0056] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 g of commercially available, thiol group-terminatedpoly(methyl methacrylate) (average molecular weight 12,000) wasdissolved in 500 g of tetrahydrofuran purified by distillation in anargon atmosphere.

[0057] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreacted poly(methylmethacrylate) was removed by filtration, the particles were washed withtetrahydrofuran and then dried to give coated particles with the surfacethereof partially modified by the insulating organic compound.

EXAMPLE 3

[0058] In a 500-mL separable flask equipped with a four-necked separablecover, stirring blade, three-way cock, condenser and temperature probe,99 g of methyl methacrylate, 1 g of methacrylic acid and 1.5 g ofthioacetic acid were stirred together at 85° C., 0.1 g of2,2′-azobisisobutyronitrile was then added, and the polymerizationreaction was allowed to proceed for 1.5 hours. After purifying anddrying, a mercapto group-terminated poly(methylmethacrylate)-methacrylic acid copolymer (average molecular weight20,000) was obtained.

[0059] The above poly(methyl methacrylate)-methacrylic acid copolymer (5g) was dissolved in 500 g of tetrahydrofuran purified by distillation inan argon atmosphere.

[0060] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreacted poly(methylmethacrylate)-methacrylic acid copolymer was removed by filtration, theparticles were washed with tetrahydrofuran and then dried to give coatedparticles with the surface thereof partially modified by the insulatingorganic compound.

EXAMPLE 4

[0061] In a 500-mL separable flask equipped with a four-necked separablecover, stirring blade, three-way cock, condenser and temperature probe,5 millimoles of mercaptopropionic acid was dissolved in 500 mL oftetrahydrofuran purified by distillation.

[0062] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreactedmercaptopropionic acid was removed by filtration, the particles werewashed with tetrahydrofuran, then dried and again dispersed in 500 mL oftetrahydrofuran.

[0063] To this dispersion was added 5 g of commercially available, epoxygroup-terminated poly(methyl methacrylate) (molecular weight 15,000) inan argon atmosphere, and the resulting mixture was stirred at 40° C. for12 hours. The unreacted poly(methyl methacrylate) was removed byfiltration, the particles were washed with tetrahydrofuran and thendried to give coated particles with the surface thereof partiallymodified with the insulating organic compound.

EXAMPLE 5

[0064] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 millimoles of mercaptoundecanol was dissolved in500 mL of tetrahydrofuran purified by distillation.

[0065] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreactedmercaptoundecanol was removed by filtration, the particles were washedwith tetrahydrofuran, then dried and again dispersed in 200 mL ofdistilled water.

[0066] To this dispersion was added 5 moles of hydroxymethylmethacrylate and, after thorough stirring, 10 g of a 0.1 mol/L cerricammonium nitrate solution prepared by using a 1 N aqueous nitric acidsolution, and the mixture was stirred for 10 hours. The mixture wasfiltered, and the particles were washed with methanol and then dried togive coated particles with the surface thereof partially modified withthe insulating organic compound.

EXAMPLE 6

[0067] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 millimoles of mercaptophenol was dissolved in 200mL of tetrahydrofuran purified by distillation.

[0068] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreacted mercaptophenolwas removed by filtration, the particles were washed withtetrahydrofuran and then again dispersed in 500 mL of purified toluene.

[0069] To this dispersion was added 5 millimoles of2-(4-chlorosulfonyl)ethyltrichlorosilane, and the mixture was stirred at40° C. for 6 hours. The unreacted2-(4-chlorosulfonyl)ethyltrichlorosilane was removed by filtration, andthe particles were washed with toluene and again dispersed in purifiedtoluene in an argon atmosphere.

[0070] To this dispersion were added 10 millimoles of copper bromide, 20millimoles of 4,4′-di-n-heptyl-2,2′-bipyridine, 5 moles of methylmethacrylate and 2.5 millimoles of p-toluenesulfonyl chloride in anargon atmosphere, and the mixture was stirred at 90° C. for 12 hours.After cooling to room temperature, 100 g of n-hexane was added, and theparticles were filtered off, further washed with n-hexane and dried togive coated particles with the surface thereof partially modified withthe insulating organic compound.

EXAMPLE 7

[0071] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 millimoles of mercaptophenol was dissolved in 500mL of tetrahydrofuran purified by distillation.

[0072] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreacted mercaptophenolwas removed by filtration, the particles were washed withtetrahydrofuran and then again dispersed in 500 mL of purifiedtetrahydrofuran.

[0073] To this dispersion was added 5 millimoles of(p-chloromethyl)phenyltrichlorosilane, and the mixture was stirred at40° C. for 6 hours. The unreacted (p-chloromethyl)phenyltrichlorosilanewas removed by filtration, the particles were washed with toluene andagain dispersed in purified tetrahydrofuran. To this dispersion wasadded 100 millimoles of sodium N,N-diethyldithiocarbamate, and themixture was stirred at room temperature for 18 hours. The unreactedsodium N,N-diethyldithiocarbamate was removed by filtration, theparticles were washed with toluene and again dispersed in purifiedtoluene in an argon atmosphere. To this dispersion were added 2millimoles of methyl methacrylate and 0.02 millimole of methacrylic acidin an argon atmosphere, and the mixture was irradiated with light from ahigh-pressure mercury lamp (product of SEN Light: HLR 100T-1) used as alight source with stirring at 40° C. for 3 hours. After cooling to roomtemperature, the particles were filtered off, washed with n-hexane anddried to give coated particles with the surface thereof partiallymodified with the insulating organic compound.

EXAMPLE 8

[0074] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 millimoles of mercaptoundecanol having a thiolgroup was dissolved in 500 mL of tetrahydrofuran purified bydistillation.

[0075] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreactedmercaptoundecanol was removed by filtration, the particles were washedwith tetrahydrofuran, then dried and dispersed in 500 mL of toluene.

[0076] To this dispersion was added 5 millimoles of2-norbornene-6-methyldichlorosilane, and the reaction was carried outwith stirring at 40° C. for 6 hours for conversion of the hydroxyl groupto the norbornene group. The unreacted2-norbornene-6-methyldichlorosilane was removed by filtration, and theparticles were washed with toluene and again dispersed in 500 mL ofpurified toluene in an argon atmosphere. To this dispersion was added 5millimoles of bis(tricyclohexylphosphine)benzylideneruthenium(IV)dichloride as a metathesis polymerization catalyst, and the reaction wascarried out at room temperature for 30 minutes for conversion of thenorbornene group to the ruthenium carbene group. The unreactedbis(tricyclohexylphosphine)benzylideneruthenium(IV) dichloride wasremoved by filtration, the particles were washed with toluene and againdispersed in 400 mL purified toluene in an argon atmosphere. To thisdispersion was added, as a monomer to be subjected to graftpolymerization, 2 millimoles of norbornene dissolved in 100 mL ofpurified toluene in an argon atmosphere, and the graft polymerizationwas carried out at room temperature for 30 minutes. The particles werefiltered off, washed with methanol and then dried to give coatedparticles with the surface thereof partially modified with theinsulating organic compound.

EXAMPLE 9

[0077] Styrene (500 millimoles), 5 millimoles ofmethacryloyloxyphenyldimethylsulfoniummethylsulfate, 5 millimoles of2,2′-azobis(2-amidinopropane) dihydrochloride and 250 mL of distilledwater were weighed and placed in a 1,000-mL separable flask equippedwith a four-necked separable cover, stirring blade, three-way cock,condenser and temperature probe, and the mixture was stirred at 200 rpmand the polymerization was carried out at 60° C. for 7 hours in anitrogen atmosphere to give an 18% dispersion of latex particles havingsulfonium groups on the surface thereof and having an average particlediameter of 220 nm.

[0078] The above latex particle dispersion was diluted to 1% withdistilled water, 10 g of gold-plated particles with a particle size of 5μm were dispersed in 500 mL of the dilution in an argon atmosphere, andthe mixture was stirred at 40° C. for 12 hours. The mixture was filteredthrough a 3-μm-mesh filter, and the particles were further washed withmethanol and dried to give coated particles with the surface thereofpartially modified with the insulating organic particles.

EXAMPLE 10

[0079] Styrene (500 millimoles), 1.92 millimoles of sodiump-styrenesulfonate, 0.94 millimole of potassium persulfate and 475 mL ofdistilled water were weighed and placed in a 100-mL separable flaskequipped with a four-necked separable cover, stirring blade, three-waycock, condenser and temperature probe, and the mixture was stirred at200 rpm and the polymerization was carried out at 60° C. for 12 hours ina nitrogen atmosphere to give a 10% dispersion of latex particles havingsulfonic acid groups on the surface thereof and having an averageparticle diameter of 105 nm.

[0080] The above latex particle dispersion was diluted to 1% withdistilled water, 10 g of gold-plated particles with a particle size of 5μm were dispersed in 500 mL of the dilution in an argon atmosphere, andthe mixture was stirred at 40° C. for 12 hours. The mixture was filteredthrough a 3-μm-mesh filter, and the particles were further washed withmethanol and dried to give coated particles with the surface thereofpartially modified with the insulating organic particles.

EXAMPLE 11

[0081] Styrene (250 millimoles), 250 millimoles of glycidylmethacrylate, 5 millimoles of 2,2′-azobis(2-amidinopropane)dihydrochloride and 549 mL of distilled water were weighed and placed ina 100-mL separable flask equipped with a four-necked separable cover,stirring blade, three-way cock, condenser and temperature probe, and themixture was stirred at 200 rpm and the polymerization was carried out at70° C. for 2 hours in a nitrogen atmosphere. Then, 40 millimoles ofglycidyl methacrylate was added, and the polymerization was carried outfor further 12 hours to give a 10% dispersion of latex particles havingsulfonic acid groups on the surface thereof and having an averageparticle size of 120 nm.

[0082] To this latex particle dispersion was added 250 millimoles of3-mercaptopropionic acid, and the reaction was carried out under refluxfor 5 hours. The particles were washed by centrifugation and dilutedwith distilled water to give a 10% dispersion of latex particles havingthiol groups on the surface thereof and having an average particlediameter of 120 nm.

[0083] In 100 mL of this latex particle dispersion were dispersed in anargon atmosphere 5 g of gold-plated particles with a particle size ofabout 5 μm, and the mixture was stirred at 40° C. for 12 hours. Themixture was filtered through a 3-μm-mesh filter, and the particles werefurther washed with methanol and dried to give coated particles with thesurface thereof partially modified with the insulating organicparticles.

Comparative Example 1

[0084] In a 1,000-mL separable flask equipped with a four-neckedseparable cover, stirring blade, three-way cock, condenser andtemperature probe, 5 g of poly(vinyl alcohol) (average molecular weight10,000) was dissolved in 500 g of distilled water in an argonatmosphere.

[0085] In this solution were dispersed 10 g of gold-plated particleswith a particle diameter of about 5 μm in an argon atmosphere, and themixture was stirred at 40° C. for 12 hours. The unreacted poly(vinylalcohol) was removed by filtration, the particles were washed with hotwater and then dried to give coated particles with the surface thereofwholly modified with the insulating organic compound.

Comparative Example 2

[0086] Ten grams of gold-plated particles with a particle diameter ofabout 5 μm and 5 g of a vinylidene fluoride resin were introduced into ahybridization apparatus and treated at 90° C. for 3 hours to give coatedparticles with the surface thereof partially modified with theinsulating organic compound.

Evaluations

[0087] The coated particles obtained in Examples 1 to 11 and ComparativeExamples 1 and 2 were measured for organic coating layer thickness andfor coverage, namely the percent of organic compound-coated area on themetal-surfaced particle surface.

[0088] Then, each coated particle species was treated with a jet mill(product of Nisshin Engineering: Current Jet CJ-2.5) under the action ofa force of 1 N/cm² or 5 N/cm² for conversion to a state of individualparticles occurring singly and independently, followed by coveragemeasurement. The presence or absence of aggregates after jet milltreatment was judged by the eye. The results thus obtained are shown inTable 1. Before conversion to single Presence or absence of aggregatesand particles coverage after jet mill treatment Coating organic 1 N/cm²5 N/cm² Coating organic compound species layer thickness CoverageAggregates Coverage Aggregates Coverage Example 1 Poly(vinyl alcohol) 15nm 65% Found 65% Not found 65% Example 2 Poly(methyl methacrylate) 10 nm65% Found 65% Not found 65% Example 3 Methyl methacrylate-acrylic acid15 nm 60% Found 60% Not found 60% copolymer Example 4 Poly(methylmethacrylate) 12 nm 67% Found 67% Not found 67% Example 5Poly(hydroxymethyl methacrylate) 20 nm 72% Found 72% Not found 72%Example 6 Poly(methyl methacrylate) 22 nm 80% Found 80% Not found 79%Example 7 Poly(methyl methacrylate) 25 nm 82% Found 82% Not found 81%Example 8 Poly(norbornene) 30 nm 77% Found 77% Not found 77% Example 9Surface sulfonium-polystyrene — 43% Not found 41% Not found 12%particles Example 10 Surface sulfonic acid-polystyrene — 58% Not found57% Not found 25% particles Example 11 Surface thiol-poly(methyl — 69%Not found 69% Not found 32% methacrylate) particles Compar. Ex. 1Poly(vinyl alcohol) 15 nm ˜100%  Found 65% Not found 18% Compar. Ex. 2Poly(vinylidene fluoride) 15 nm 65% Found 58% Not found 20%

[0089] As can be seen from Table 1, the coated particles obtained inComparative Examples 1 and 2 showed marked decreases in coverage in thestep of conversion to single individual particles whereas the decreasesin coverage were small with the coated particles obtained in Examples 1to 11; in particular, the coated particles obtained in Examples 1 to 8showed almost no decreases in coverage.

[0090] Even when jet mill treatment was carried out with a small force,no aggregates were observed among the coated particles obtained inExamples 9 to 11.

Industrial Applicability

[0091] The present invention, which has the constitution describedabove, can provide coated particles excellent in the reliability ofconnection.

1. A coated particle, which comprises a metal-surfaced particle as acore and results from a partial modification of the surface thereof withan organic compound via a functional group (A) capable of binding to ametal.
 2. The coated particle according to claim 1, wherein the surfaceof the metal-surfaced particle has the organic compound grafted thereon.3. The coated particle according to claim 1 or 2 wherein the surface ofthe metal-surfaced particle serving as a core is partially modified withan organic compound by introducing thereonto a compound having apolymerizing or chain-transferring functional group or catalyst moiety(C), followed by graft polymerization with each polymerizing orchain-transferring functional group or catalyst moiety (C) site servingas an initiation site.
 4. The coated particle according to claim 3,wherein the graft polymerization is carried out in the manner ofring-opening metathesis polymerization.
 5. The coated particle accordingto claim 1, which comprises the metal-surfaced particle as the core andresults from a partial modification of the surface thereof particle withan organic particle containing a functional group (A) capable of bindingto a metal.
 6. The coated particle according to claim 1, 2, 3, 4 or 5,wherein the organic compound has a positive or negative charge.
 7. Thecoated particle according to claim 1, 2, 3, 4, 5 or 6, wherein theorganic compound is an insulating compound.